The present invention relates generally to photography, and more specifically to photography using a remote control to operate a camera from a distance.
Many modem cameras allow the use of a remote control for initiating a photograph of a scene. This capability is especially useful when the photographer wishes to include himself in the photograph. In a typical case, the camera may be placed on a tripod or other stationary surface and positioned to view the desired scene. The photographer can move into position in the composed scene and then use the remote control to cause the camera to take the photograph. The remote control is often a small handheld unit that sends an infrared light signal when a button is pressed by the user. The signal is directed toward the camera that has a special sensor to detect the signal from the remote control.
In a simple embodiment, the camera performs exactly the same sequence of operations when taking a photograph under remote control as when the shutter release button on the camera is pressed by the user directly.
Many modem cameras also include automatic focusing capability. Typically the camera projects an image of a portion of the scene onto an electronic sensor and then moves some part of the camera optics in order to maximize the contrast of the image portion read by the sensor, thereby achieving focus. In a digital camera, the same electronic sensor may be used for focus determination as for taking the actual resulting photograph or separate sensors may be provided. In a film camera, the electronic sensor may be used for focusing and light metering, but is not involved in the actual taking of the photograph. Even in a film camera, the sensor may be capable of sensing one or more selected portions of the scene image.
Often, a scene contains a particular point of interest that the photographer wishes to ensure is in focus in a photograph. For example, when a photograph includes people, it is usually desirable for the people to be sharply focused.
Typically, a camera will use a small portion of a scene for determining focus. This xe2x80x9cfocus regionxe2x80x9d is often in the center of the camera""s field of view. Some cameras allow the photographer to select a focus region at some other location besides the center of the camera""s field of view to accommodate the situation where the point of interest in the scene is not in the center of the resulting photograph. When the focus region is aligned with the point of interest in the scene, the camera will be able to focus on the desired part of the scene and produce the desired photograph.
During automatic operation, a camera typically chooses a focus region in the center of its field of view. When the camera is being operated by a remote control, the photographer is at a distance from the camera, and therefore cannot view the scene through the camera""s viewfinder nor operate the camera controls to select a different focus point.
This combination of circumstances can cause a difficulty in obtaining the desired or expected photographic result in some cases.
FIG. 2 depicts a scene that may cause difficulty when photographed with a camera under remote control. The camera focus region is indicated by brackets (202). During automatic operation, the camera will focus on the objects in the focus region. These objects are relatively distant from the camera. The photographer (201) operating the camera by remote control is outside the focus region and will not be taken into account during focusing. Being relatively closer to the camera, the photographer will be out of focus in the resulting photograph. Generally, it is preferable to have the person sharply focused in the photograph.
Several alternatives exist for causing the camera to take the desired photograph with the person in focus.
The photographer could disable the automatic focus capability of the camera and focus manually at the proper distance before positioning himself in the scene. However this technique is prone to error and compromises the convenience of having a camera with automatic focus capability.
Some camera systems have addressed this situation by various methods.
One method described in U.S. Pat. No. 5,119,123 limits the range of focus distances that the camera will consider when used with a remote control, and also sets the camera aperture to maximize the depth of field in the resulting photograph so as to increase the likelihood that the desired subject is in focus. However, this method limits the photographer""s choices for scene composition and for creative photographic effects.
Another method described in Japanese Patent 04371938 has the camera warn the photographer when the focus distance determined automatically by the camera is greater than would likely occur during remote control operation. The photographer can then reposition himself and attempt the photograph again. However, this method limits the photographer""s choices for scene composition and may require multiple attempts to obtain a successful photograph.
Still another method as described in Japanese Patents 63237674 and 07159678 uses the difference in arrival times of an infrared and an ultrasonic signal sent simultaneously by the remote control to calculate the distance between the remote control and the camera. This distance is then used to determine the lens position for proper focus. However, this method requires the added expense of two kinds of signaling paths and may be subject to errors when the remote control is significantly off-center in the camera field of view.
Other prior solutions may require multiple signaling devices or may be complex for the photographer to use.
What is needed is a simple, inexpensive system or method for causing a camera to reliably select the correct focus region when used with a remote control, while preserving the photographer""s range of choices of scene composition and creative photographic effects.
A camera system uses a xe2x80x9cfocus attractingxe2x80x9d remote control. The remote control signals its position in the camera""s field of view by emitting a distinguishable light signal. The camera selects a focus region at the position indicated by the remote control and performs its automatic focus function. Objects in the vicinity of the remote control are sharply focused in the resulting photograph.